Human AIDS presents a mysterious problem, whose understanding at the biologic level would benefit from study of a reasonable animal model. To date, however, human AIDS has not proven transmissable to animals, so access to a spontaneous AIDS-like animal disease would be all the more helpful. We have described the recurrent outbreaks of an AIDS-like problem (called SAIDS for simian AIDS) occurring spontaneously in rhesus monkeys at the California Primate Center (CPRC). More recently we have found that SAIDS, including Kaposi-like skin lesions, is experimentally transmissable to monkeys at both the CPRC and NIH. Inocula giving rise to the disease include, not only tissue extracts, but also whole blood and filtered plasma. Although infectious CMV is present in the donor and recipient monkeys, purified SAIDS-CMV has not as yet induced the disease nor has CMV been isolated from the infective plasma. Thus, as with human AIDS, there may be another etiologic agent acting synergistically or independently of CMV. The ready transmissability of SAIDS, both under natural cage exposure conditions and after inoculation, affords the opportunity to identify and characterize the etiologic agent(s) (specific aim #1), to work out the natural history and pathogenesis (specific aim #2) and to develop effective means of treatment and prevention (specific aim #3). Knowledge gained from this animal model system may have direct applicability to the human situation and should lead to an improved understanding of the primate immune system and its functional impairment by this type of acquired infection.